The present invention relates to a device for exhaust-gas purification involving reduction of nitrogen oxides, which are present in the exhaust gas from internal combustion engines, in particular for motor vehicles, by way of ammonia in an SCR catalytic converter, and to a method for operating and monitoring a device of this type.
Devices which operate with SCR catalytic converters (Selective Catalytic Reduction catalytic converters), are disclosed, for example, in DE 297 08 591 U1. Particularly when used in motor vehicles, devices of this type have to satisfy particular demands with regard to the space taken up, the ability for spontaneous response and the ability to adapt to constantly changing working conditions, as well as operational safety.
In connection with operation safety, substances or substance mixtures which release ammonia through thermolysis are used as the ammonia source, which has the effect of requiring an increased amount of space, because the ammonia which can be used for the reduction constitutes only a fraction of the starting material. Moreover, spontaneous response requires a sufficiently large reservoir or temporary store volume for the ammonia which has been released in gas form. All this is associated with corresponding safety requirements.